Work on the three dimensional structure of chicken troponin-C will continue. Attempts will be made to obtain heavy atom isomorphous derivatives. These will then be used to construct an electron density map of the protein at low resolution. The work will then be extended to high resolution. Crystallization of cardiac troponin-C and troponin-T will be attempted. Experiments will be conducted to determine the iodination patterns of the specific tyrosines in the thin filament complex.